Which of the following best explains why water molecules orient differently around a…
CHEMISTRY · Single correct · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
Which of the following best explains why water molecules orient differently around a K⁺ ion compared with a Br⁻ ion in aqueous solution?
(a) K⁺ is smaller than Br⁻, so water cannot approach as closely, causing the dipoles to orient opposite to those around Br⁻.
(b) Water forms hydrogen bonds only with Br⁻, so oxygen atoms point toward Br⁻ while hydrogens point toward K⁺.
(c) K⁺ carries positive charge, so the partial negative oxygen faces it, whereas Br⁻ carries negative charge, so the partial positive hydrogens face it.
(d) Br⁻ has a much larger electron cloud that repels water’s lone-pair electrons, forcing the hydrogens to point inward while the oxygens point outward; the opposite occurs for K⁺.